Tetraena

Tetraena is a genus of flowering plants in the family Zygophyllaceae.

Description
Species of Tetraena are shrubby or herbaceous, the tallest being around 1.5 m. The leaves are opposite, or sometimes borne on short shoots and then appearing to be alternate. They may or may not have stalks (petioles). The flower usually has five petals and five sepals, rarely four, and ten stamens. The flower is usually tube-like in appearance with white to pale orange petals. The ovary has three to five chambers (locules). The ripe fruit is variable in shape, splitting into parts before releasing the seeds.

Taxonomy
The genus Tetraena was erected by Karl Maximovich in 1889 for the species Tetraena mongolica. Until 2003, this was the only species recognized in the genus. Molecular phylogenetic studies suggested that the genus Zygophyllum was not monophyletic, since Tetraena and some other genera were nested within it. To create monophyletic genera, Björn-Axel Beier and Mats Thulin transferred about 40 species of Zygophyllum to Tetraena, creating a much expanded genus, though IPNI still treats it as a synonym of Zygophyllum.

Species
, Plants of the World Online accepted the following species:


 * Tetraena aegyptia (Hosny) Beier & Thulin
 * Tetraena alba (L.f.) Beier & Thulin
 * Tetraena applanata (Van Zyl) Beier & Thulin
 * Tetraena bucharica (B.Fedtsch.) Beier & Thulin
 * Tetraena chrysopteros (Retief) Beier & Thulin
 * Tetraena clavata (Schltr. & Diels) Beier & Thulin
 * Tetraena coccinea (L.) Beier & Thulin
 * Tetraena cornuta (Coss.) Beier & Thulin
 * Tetraena cylindrifolia (Schinz) Beier & Thulin
 * Tetraena decumbens (Delile) Beier & Thulin
 * Tetraena dumosa (Boiss.) Beier & Thulin
 * Tetraena fontanesii (Webb & Berthel.) Beier & Thulin
 * Tetraena gaetula (Emb. & Maire) Beier & Thulin
 * Tetraena geslinii (Coss.) Beier & Thulin
 * Tetraena giessii (Merxm. & A.Schreib.) Beier & Thulin
 * Tetraena hamiensis (Schweinf.) Beier & Thulin
 * Tetraena longicapsularis (Schinz) Beier & Thulin
 * Tetraena longistipulata (Schinz) Beier & Thulin
 * Tetraena madagascariensis (Baill.) Beier & Thulin
 * Tetraena madecassa (H.Perrier) Beier & Thulin
 * Tetraena mandavillei (Hadidi) Beier & Thulin
 * Tetraena microcarpa (Licht. ex Cham.) Beier & Thulin
 * Tetraena migiurtinorum (Chiov.) Beier & Thulin
 * Tetraena mongolica Maxim.
 * Tetraena prismatica (Chiov.) Beier & Thulin
 * Tetraena prismatocarpa (Sond.) Beier & Thulin
 * Tetraena propinqua (Decne.) Ghaz. & Osborne
 * Tetraena pterocaulis (Van Zyl) Beier & Thulin
 * Tetraena qatarensis (Hadidi) Beier & Thulin
 * Tetraena retrofracta (Thunb.) Beier & Thulin
 * Tetraena rigida (Schinz) Beier & Thulin
 * Tetraena simplex (L.) Beier & Thulin
 * Tetraena somalensis (Hadidi) Beier & Thulin
 * Tetraena stapfii (Schinz) Beier & Thulin
 * Tetraena tenuis (R.Glover) Beier & Thulin

Distribution
Tetraena is native from the Canary Islands in the west and South Africa in the south to China in the east.